Forget Napster and Java. The most revolutionary technologies often attract the fewest headlines. Here are two innovations that set the business agenda.

How SIG-nificantWHAT The signature file, better known as the “sig file” — a few lines of text appended to e-mail messagesWHEN Circa 1980WHERE Probably somewhere on FidoNet, or some other early online bulletin boards that gave way to UsenetWHO Unknown. Sig files are so easy to create, no self-respecting nerd has stepped forward to claim parentage.

If e-mail is the Internet’s killer app, the signature file represents the assassin’s initials etched on the bullet. Sig files describe who the sender is — job title, phone number, and so on. But they also reveal what the sender is about, because the essence of a sig file is the digital sound bite affixed below one’s coordinates. Some choose an inscrutable observation: “Everywhere is walking distance if you have the time.” Others go for inspiration: “All people smile in the same language.”

Standing at the juncture of the oldest instinct for self-expression and the newest zeal for self-promotion, the sig file is a perfect embodiment of the New Economy. Sig files signify status. In the egalitarian world of cyberspace, nobody knows whether you’re a dog or a CEO. The sig file tells where you stand. And those little quotations, seemingly so benign, reflect a deeper human yearning in the tradition of “Kilroy was here!” which scrawled out proof that you existed.